The present invention relates to apparatus for glossing sheets, and more particularly, to apparatus for glossing developer sheets.
Apparatus for the application of heat to coated substrates are known. For example, see U.S. Pat. Nos. 1,399,160; 1,913,704; 3,349,222; 3,478,665; 3,517,164; 3,621,201; 3,857,189; 3,902,041; 4,021,641; 4,059,394; 4,147,922; 4,464,561; 4,537,492; and 4,596,920.
A coated substrate such as a developer sheet is typically heated in order to provide a glossy finish thereon. Such developer sheets are used in conjunction with conventional pressure-sensitive copy paper or photosensitive imaging systems employing microcapsules to provide visible images upon contact with a color former which is image-wise released from the microcapsules and transferred to the developer sheet.
Photosensitive imaging systems employing microencapsulated radiation sensitive compositions are the subject of commonly assigned U.S. Pat. Nos. 4,399,209 and 4,440,846 as well as copending U.S. patent application Ser. No. 339,917, filed Jan. 18, 1982. These imaging systems are characterized in that an imaging sheet including a layer of microcapsules containing a photosensitive composition in the internal phase is image-wise exposed to actinic radiation. In the most typical embodiments, the photosensitive composition is a photopolymerizable composition including a polyethylenically unsaturated compound and a photoinitiator and is encapsulated with a color former. Exposure image-wise hardens the internal phase of the microcapsules.
U.S. Pat. No. 4,399,209 discloses a transfer system in which the imaging sheet is assembled with a developer sheet prior to being subjected to a rupturing force. Upon passing through the development station in contact with the developer sheet, the microcapsules rupture and image-wise release the internal phase whereupon the color former migrates to the developer sheet where it reacts with a dry developer and forms a color image. The imaging system can be designed to reproduce monochromatic or polychromatic full color images.
Apparatus for glossing the developer sheets of the foregoing imaging systems are becoming known. Commonly assigned U.S. patent application Ser. No. 017,102, filed Feb. 19, 1987 discloses an apparatus for glossing the developer sheets wherein a developer sheet is fed between the convex side of a heated plate and a continuous belt held snugly against the convex side of the plate; the thermoplastic resin side of the developer sheet is adjacent to the belt. Commonly assigned U.S. patent application Ser. No. 016,311, filed Feb. 19, 1987 discloses an apparatus for glossing the developer sheets wherein a developer sheet is fed between a heated belt and a source of radiant energy disposed within a reflector; the thermoplastic resin side of the developer sheet is adjacent to the source of radiant energy. A commonly developed apparatus for glossing the developer sheets is disclosed at #27660, Research Disclosure (April 1987) wherein a developer sheet is fed between a heated driven roller and an idler roller. Also, a developer sheet can be glossed by placing in a hot oven.
Known processes for glossing sheets suffer from numerous disadvantages. Thermoplastic resins, which are capable of forming a film upon the application of heat, are extremely sticky compared to dry silver film, conventional film, and xerographic copies; thus, the release conditions of the sheet surface are more critical. In hot roller glossing methods, the high contact pressure may cause adhesion of the thermoplastic resin to the hot rollers. In methods involving heated surfaces, adhesion of the thermoplastic resin may also be a problem. Also, known glossing methods do not achieve an even gloss with respect to image density and are also slow. Additionally, the energy requirements of glossing processes are higher than known photographic, glossing, and xerographic toner fusing technologies.
Thus, a need exists in the art for an apparatus for glossing sheets wherein no adhesion of the thermoplastic resin to another surface results and a high throughput is achieved.